There is known a head-mounted device (HMD), which is worn on a head of a user and is capable of displaying a virtual space image. In Patent Document 1, there is described a design assistance system having a viewpoint information display function for assisting in design of a property, for example, a building, using a virtual space. In Patent Document 1, as means for changing a viewpoint position in real time, in addition to related-art means for allowing a user to operate a group of operation buttons to walk through the virtual space forward/backward or leftward/rightward, there is a description of means for allowing the user to input a viewpoint position using a plan view display unit to instantaneously move the viewpoint position, and to change a visual-field angle to change a scale to be used when a movement amount of the user in a real space is transformed into a movement amount in the virtual space.